I didn't know I had to prune in January, so I pruned in May. The plant is growing but has no flowers. My second plant that I just bought and transplanted now has yellow leaves and I don't know why.
Two Hibiscus Plant Problems
Certified GKH Gardening Expert
The first plant may need some fertilizer. If you have not done that yet, give it some fertilizer. This article has some other suggestions about what might be causing the lack of flowers:
The first plants sounds like it might be in transplant shock. This article will help with that: